Solar cell and photovoltaic module

Abstract

The invention discloses a solar cell and a photovoltaic module, relates to the photovoltaic field, and is used for solving the problem that the protection effect of a water film on a cell piece is poor in the preparation process. The solar cell comprises a silicon substrate, wherein the silicon substrate comprises a first surface and a second surface opposite to each other and a first side surface connecting the first surface and the second surface; the edge, connected with the first side face, of the first face is a groove area, the groove area is provided with a plurality of grooves, and the grooves are distributed in the length direction of the edge. When the second surface of the solar cell is cleaned or etched, the second surface is in contact with liquid, meanwhile, a water film is formed on the first surface of the solar cell, the edge of the first surface is provided with a groove, the water film on the first surface can be retained in the groove, and the water film is prevented from falling off from the first surface through the groove, so that the water film is prevented from falling off. The protection effect of the water film on the first surface is improved, so that excessive cleaning or etching of liquid below the solar cell on the first surface is reduced.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a solar cell and a photovoltaic module. Background Art

[0002] During the production of solar cells, silicon wafers need to undergo multiple process steps such as cleaning, texturing, doping, and etching. Among them, when using the "floating on water" method or chain etching equipment to perform process steps such as cleaning and etching on the cell, the "floating on water" method is that the cell floats on a wet liquid (cleaning liquid or etching liquid) and the lower surface and side surfaces of the cell in contact with the liquid are cleaned or etched by the wet liquid; at the same time, a water film needs to be formed on the upper surface of the cell facing away from the lower liquid surface to protect the upper surface of the cell from contacting the liquid below, to avoid excessive cleaning or etching of the upper surface of the cell, which affects the performance of the cell. However, the water film on the cell has a poor protective effect. Summary of the Invention

[0003] The object of the present invention is to provide a solar cell to improve the protective effect of the water film on the cell sheet and reduce the adverse effects on the performance of the solar cell.

[0004] In a first aspect, the present invention provides a solar cell comprising a silicon substrate, the silicon substrate comprising a first surface and a second surface opposite to each other, and a first side surface connecting the first surface and the second surface;

[0005] The edge of the first surface connected to the first side surface is a groove area, and the groove area includes multiple grooves, and the multiple grooves are arranged along the length direction of the edge; the grooves include continuous strip grooves or multiple discontinuous grooves.

[0006] When using the above technical solution, the edge of the first surface of the silicon substrate of the solar cell that meets the first side surface forms a groove region, and the groove region includes multiple grooves arranged along the length of the edge. That is, the edge of the first surface has grooves. Therefore, when the second surface of the solar cell is cleaned or etched, the second surface of the solar cell is brought into contact with liquid to clean or etch the second surface. Simultaneously, a water film forms on the first surface of the solar cell. Because the edge of the first surface has grooves, the water film on the first surface can be retained in the grooves. The grooves prevent the water film from falling from the first surface, thereby enhancing the water film's protective effect on the first surface, reducing the possibility of liquid from beneath the solar cell spilling onto the first surface and causing excessive cleaning or etching of the first surface, thereby reducing adverse effects on the performance of the solar cell.

[0007] In some possible implementations, an angle is formed between an extension direction of the groove and an edge where the first surface and the first side surface meet, and the angle ranges from 30° to 70°.

[0008] In some possible implementations, in a direction perpendicular to the first side surface, a width of the groove region is less than or equal to 100 μm.

[0009] In some possible implementations, the depth of the groove in the thickness direction of the silicon substrate is less than or equal to 3 μm.

[0010] In some possible implementations, the first surface has a plurality of first pyramid structures located within the groove and a plurality of second pyramid structures located outside the groove, and one-dimensional dimensions of the first pyramid structures are greater than one-dimensional dimensions of the second pyramid structures.

[0011] In some possible implementations, the solar cell further includes a functional layer disposed on the first surface; a thickness of the first functional layer located within the groove is greater than a thickness of the functional layer located outside the groove.

[0012] In some possible implementations, along a direction away from the silicon substrate, the functional layer includes a first passivation anti-reflection layer, and the first passivation anti-reflection layer includes a first aluminum oxide layer and a first silicon nitride layer that are stacked;

[0013] The thickness of the first aluminum oxide layer located in the groove is 4.5 nm to 5 nm, and the thickness of the first aluminum oxide layer located outside the groove is 4 nm to 4.5 nm;

[0014] And / or, the thickness of the first silicon nitride layer within the groove is 68 nm to 73 nm, and the thickness of the first silicon nitride layer outside the groove is 65 nm to 70 nm.

[0015] In some possible implementations, the solar cell further includes a second passivation anti-reflection layer of the doped conductive layer disposed on the second surface, and the second passivation anti-reflection layer is located on a side of the doped conductive layer facing away from the silicon substrate.

[0016] In some possible implementations, the solar cell also includes a tunneling oxide layer arranged on the second surface, the tunneling oxide layer is located between the silicon substrate and the doped conductive layer, the tunneling oxide layer and the doped conductive layer constitute a tunneling passivation contact structure, and the tunneling passivation contact structure partially or entirely covers the second surface.

[0017] In some possible implementations, a doped conductive layer and a second passivation anti-reflection layer are also provided on the first side, the doped conductive layer partially covers the first side, the second passivation anti-reflection layer completely covers the first side, and the doped conductive layer located on the first side is connected to the doped conductive layer located on the second side.

[0018] In some possible implementations, along the thickness direction of the silicon substrate, the width of the doped conductive layer located on the first side surface accounts for 10% to 20% of the thickness of the solar cell.

[0019] In some possible implementations, the area on the first side surface covered with the doped conductive layer includes at least a plurality of tower base structures, and the area on the first side surface not covered with the doped conductive layer includes at least a plurality of pyramid structures.

[0020] In a second aspect, the present invention further provides a photovoltaic module, comprising:

[0021] A battery string, wherein the battery string is formed by electrically connecting a plurality of solar cells as described in any one of the above items;

[0022] an interconnection member electrically connected to the solar cell;

[0023] and an encapsulation layer covering the surface of the battery string.

[0024] Since the photovoltaic assembly includes the solar cell of the first aspect, it has the same beneficial effects as the first aspect, which will not be described in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 A scanning electron microscope image of the first surface of a solar cell provided by an embodiment of the present invention;

[0027] Figure 2 A schematic structural diagram of a first surface of a solar cell provided by an embodiment of the present invention;

[0028] Figure 3 A schematic cross-sectional view perpendicular to the side of a solar cell provided by an embodiment of the present invention;

[0029] Figure 4 This is a scanning electron microscope image of the laser thermal cracking surface of a solar cell provided in an embodiment of the present invention.

[0030] Figure numerals: 10 is a silicon substrate, 11 is a first surface, 12 is a first side surface, 121 is a side Poly region, 13 is a groove region, 14 is a groove, 15 is a second surface, 20 is a tunneling oxide layer, 30 is a doped conductive layer, 40 is a second aluminum oxide layer, 50 is a second silicon nitride layer, 60 is a first aluminum oxide layer, and 70 is a first silicon nitride layer. DETAILED DESCRIPTION

[0031] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0033] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined. "Several" means one or more, unless otherwise specifically defined.

[0034] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0035] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and may encompass internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0036] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a solar cell, including a silicon substrate 10, the silicon substrate 10 includes a first surface 11 and a second surface 15 relative to each other and multiple side surfaces connecting the first surface 11 and the second surface 15, wherein the multiple side surfaces include a first side surface 12; the edge of the first surface 11 connected to the first side surface 12 is a groove area 13, the groove area 13 includes a plurality of grooves 14, and the plurality of grooves 14 are arranged along the length direction of the edge.

[0037] The present application has found that: before preparing a solar cell, the portion near the edge area on the first surface 11 of the silicon substrate 10 is heat-treated, specifically by using a non-destructive laser for heat treatment; during the cleaning or etching process in the preceding steps of making a solar cell, the area of ​​the first surface 11 that has been heat-treated will form a groove 14 after chemical cleaning or etching. The groove 14 can protect the water film at the edge of the first surface 11 during the wet process steps in the subsequent steps of the battery. The study found that the reason for the formation of the groove 14 is that after being acted upon by appropriate laser energy, dislocations and the like occur inside the silicon substrate. When corroded by chemical liquids, the corrosion rates are different and the groove 14 is eventually formed. In addition, different laser heat treatment processes will also bring different groove morphological characteristics, and different groove morphological characteristics have different protective effects on the water film. Therefore, the present application optimizes the laser heat treatment process so that the morphological characteristics of the groove are consistent with the protective effect on the water film while reducing the impact on battery efficiency.

[0038] It should be noted that before preparing the solar cell, part of the edge area on the first surface 11 of the silicon substrate 10 is heat-treated. Specifically, the edge of the first surface 11 of the conventional silicon substrate 10 can be directly laser-heat-treated, and the area near the edge of the silicon substrate 10 is the laser-heat-treated area, and the first side surface 12 near the edge is the side surface formed by mechanical cutting, such as wire cutting. In addition, the conventional silicon substrate 10 can also be laser-treated and then split, and the edge formed after the split is the newly generated edge of the silicon substrate 10; the area near the newly generated edge on the first surface 11 of the silicon substrate 10 is the heat-treated area; and the first side surface 12 near the newly generated edge is the laser-heat-cracked surface.

[0039] Take the example of laser processing a conventional silicon substrate 10 and then splitting it into a sliced ​​silicon substrate 10. When preparing a sliced ​​solar cell, the whole silicon wafer is first cut into several equal parts. After the sliced ​​cell slices are prepared, a cell string is formed, and then laminated to form a photovoltaic module. The present application first prepares sliced ​​silicon wafers, and then prepares sliced ​​cells. Among them, the whole silicon wafer is first cut at the position to be cut by a first laser to form a guide groove, and then a second laser is used to perform heat treatment along the direction of the guide groove, and finally mechanically split to obtain a sliced ​​silicon wafer with a new side. The edge area on the first side of the sliced ​​silicon wafer close to the newly generated side is the laser heat treatment area.

[0040] When the above technical solution is used, during the preliminary steps of preparing a solar cell, after the first surface 11 of the silicon wafer has completed the relevant cleaning or etching operations, grooves 14 are formed on the edge of the first surface 11 that has undergone the aforementioned heat treatment. Specifically, a groove region 13 is formed at the edge of the first surface 11 of the silicon substrate 10 that meets the first side surface 12. The groove region 13 includes a plurality of grooves 14 arranged along the length of the edge.

[0041] Afterwards, in the process of continuing to prepare the solar cell, when cleaning or etching the second surface 15, the second surface 15 is placed face down in contact with the liquid used for cleaning or etching, such as by using a "floating on water" method or on a chain etching device, to clean or etch the second surface, thereby forming a water film on the first surface 11. Since the edge of the first surface 11 has a groove 14, the water film on the first surface 11 can remain in the groove 14, and the groove 14 prevents the water film from falling from the first surface 11, thereby maintaining the continuity and integrity of the water film on the first surface 11, and improving the protective effect of the water film on the first surface 11, thereby reducing the excessive cleaning or etching of the first surface 11 by the liquid under the silicon substrate 10 from overflowing onto the first surface 11, thereby reducing the adverse effects on the solar cell preparation process.

[0042] It should be noted that the first surface 11 of the silicon substrate 10 can be the light-receiving surface (i.e., the front surface) of the solar cell, and the second surface 15 can be the backlight surface (i.e., the back surface) of the solar cell. Alternatively, the first surface 11 of the silicon substrate 10 can be the back surface of the solar cell, and the second surface 12 can be the front surface of the solar cell. When the laser is irradiated on the silicon wafer for heating, the first surface 11 serves as the laser incident surface.

[0043] In some embodiments, as Figure 1 As shown, each groove 14 in the groove area 13 includes a plurality of continuous strip-shaped grooves or a plurality of discontinuous grooves. The continuous strip-shaped grooves, that is, the groove 14 is in the shape of a strip as a whole, can be a groove 14 that is a continuous strip. The discontinuous grooves, that is, a groove 14 includes a plurality of grooves, and the plurality of grooves are arranged in a straight line to form a discontinuous strip. The lengths of the plurality of grooves 14 can be different or the same, and the widths of the plurality of grooves 14 (the length in the direction perpendicular to the length of the groove 14) can be the same or different. The plurality of grooves 14 are arranged at intervals along the edge length direction of the first surface 11, that is, on the first surface 11, along the length direction of the side where the first side surface 12 connects to the first surface 11, the plurality of grooves 14 are arranged at intervals on the first surface. The distance between each two adjacent grooves 14 can be equal, that is, arranged at equal intervals, or unequal, that is, arranged at unequal intervals; the widths of the grooves 14 with the same spacing distance can be equal width structures or unequal width structures.

[0044] The strip-shaped groove 14 has a large contact area with the water film, which can effectively attach the water film, improve the adhesion strength of the water film on the first surface 11, and increase the residence time of the water film on the first surface 11, thereby reducing the shedding of the water film from the first surface 11, improving the protective effect of the water film on the first surface 11, and reducing the impact on the solar cell.

[0045] In some embodiments, as Figure 2As shown, when the groove 14 is generally strip-shaped, an angle α is formed between the extending direction of the groove 14 and the edge where the first surface 11 and the first side surface 12 meet. That is, an angle α is formed between the extending direction of the groove 14 and the side of the first surface 11 corresponding to the groove 14. The angle α ranges from 30° to 70°, and can specifically be 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, etc. The angles α between different grooves 14 and the corresponding edges can be different or the same. Because the angle α is formed between the extending direction of the groove 14 and the corresponding edge of the first surface 11, the extending direction of the groove 14 is angled with the direction perpendicular to the first side surface 12. The extending direction of the groove 14 is not parallel to the direction in which the water film flows away from the edge of the first surface 11. This allows the groove 14 to further adhere to and hinder the water film in a direction perpendicular to the first side surface 12, further reducing the water film from falling off the first surface 11 and thereby improving the protective effect of the water film on the first surface 11. In this embodiment, a second laser is used to perform laser heat treatment on a conventional silicon substrate and then split it. Specifically, the second laser uses a lossless thermal cracking laser. By adjusting the laser movement speed, laser power and other process parameters of the lossless thermal cracking laser in the extension direction of the guide groove, a groove 14 with a desired angle is obtained when preparing a solar cell.

[0046] In some embodiments, as Figure 2 As shown, in the direction perpendicular to the first side surface 12, the width W of the groove region 13 is less than or equal to 100 μm. The groove region 13 is the region where all the grooves 14 close to the first side surface 12 are located. Figure 1 and Figure 2 In the area indicated by the dashed line, the width W of the groove region 13 refers to the distance, in a direction perpendicular to the first side 12, between the end of the groove 14 closest to the first side 12 and the end of the groove 14 farthest from the first side 12. Specifically, the width W of the groove region 13 can be 1 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc. If the width W of the groove region 13 is too small, the groove region 13 cannot effectively adhere to the water film and cannot effectively reduce the shedding of the water film. If the width W of the groove region 13 is greater than 100 μm, the width of the groove region 13 is too large, that is, the area of ​​the groove region 13 is too large, which may affect the strength of the solar cell and the passivation effect of the first side 11. Therefore, in order to improve the protection effect of the water film and the strength and passivation effect of the solar cell, the width W of the groove region 13 in this embodiment is selected to be less than or equal to 100 μm.

[0047] It should be noted that the distance between the groove area 13 and the first side surface 12 may be less than or equal to 10 μm, and specifically may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

[0048] In some embodiments, the depth of the groove 14 in the thickness direction of the silicon substrate 10 is less than or equal to 3 μm. Specifically, the depth of the groove 14 can be 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, etc. If the depth of the groove 14 is too small, the water film cannot be effectively attached and the shedding of the water film cannot be effectively reduced. If the depth of the groove 14 is greater than 3 μm, the depth of the groove 14 is too large, which may affect the strength of the solar cell and the passivation effect of the first surface 11. Therefore, considering the improvement of the protection effect of the water film and the strength and passivation effect of the solar cell, the depth of the groove 14 in this embodiment is selected to be less than or equal to 3 μm.

[0049] It should be noted that in some embodiments, when measuring the depth of the groove 14, the battery surface in the area where the groove 14 is located can be directly measured and calibrated using a testing instrument (optical microscope, atomic force microscope, scanning electron microscope, transmission electron microscope, etc.). In one case, the surface of the silicon substrate 10 in the area where the groove 14 is located is covered with a film layer. Since the thickness of the film layer is at the nanometer level, the surface of the non-groove area of ​​the battery can be selected as a reference plane, and the height of one or more points on the battery surface in the bottom area of ​​the groove 14 relative to the reference plane can be directly measured using a testing instrument to obtain the depth data of the groove 14. In another case, the surface of the non-groove area of ​​the battery can be selected as the reference plane, and the height data of the surface of the silicon substrate 10 in the bottom area of ​​the groove 14 relative to the reference plane can be measured. The height data can then be obtained by subtracting the film thickness data in the non-groove area of ​​the battery from the film thickness data in the groove.

[0050] Furthermore, in some embodiments, when measuring the length and width of the groove 14, in one case, since the thickness of the film layer is at the nanometer level, the length or width of the groove 14 on the battery surface can be directly measured to obtain the data. In another case, the length or width of the groove 14 on the battery surface can be measured and then the thickness of the film layer on the groove sidewall can be added to obtain the data. The above test method is only for this embodiment, and other measurement methods can also be used.

[0051] In some embodiments, the first surface 11 has a plurality of pyramid structures, and the plurality of pyramid structures include a first pyramid structure located in the groove 14 and a second pyramid structure located outside the groove 14, and the one-dimensional size of the first pyramid structure is greater than the one-dimensional size of the second pyramid structure. The pyramid structure is obtained by velveting the first surface 11, so that the first surface 11 forms a plurality of pyramid structures. The pyramid structure has a base, a top, and a plurality of sides connecting the bottom and the top, and the bottom can be an approximate rectangle or other polygon. The one-dimensional size of the pyramid structure refers to any one of the length, width or diagonal length of the base of the pyramid structure, and / or the height of the pyramid structure, and the height refers to the height from the top to the base.

[0052] For example, the bottom of the pyramid structure has a cross-section similar to a rectangle, and the one-dimensional size of the first pyramid structure located in the groove 14 is specifically as follows: the width of the bottom of the first pyramid structure is 1.5μm to 1.7μm, specifically 1.5μm, 1.55μm, 1.6μm, 1.65μm, 1.7μm, etc., and the height of the first pyramid structure is 0.9μm to 1.1μm, specifically 0.9μm, 0.95μm, 1μm, 1.05μm, 1.1μm, etc. The one-dimensional size of the second pyramid structure located outside the groove is: the width of the base of the second pyramid structure is 1.3μm to 1.5μm, specifically 1.3μm, 1.35μm, 1.4μm, 1.45μm, 1.5μm, etc.; the height of the second pyramid structure is 0.7μm to 0.9μm, specifically 0.7μm, 0.75μm, 0.8μm, 0.85μm, 0.9μm, etc.

[0053] Compared with the case where there is no pyramid structure in the groove 14, by adjusting the texturing process and additives, a pyramid structure is formed both inside and outside the groove 14 on the first surface 11. The area outside the groove 14 serves as the main light absorption area, and its reasonable pyramid structure size can increase light absorption and improve battery efficiency. When the size of the pyramid structure in the area outside the groove 14 is optimal, the process is simplified, and a pyramid structure is simultaneously formed in the groove 14 to further improve the absorption of diffusely reflected light in the groove 14. Since the size of the pyramid structure has an impact on the reflectivity, the texturing process is optimized while taking into account the size of the pyramid structure formed in the area outside the groove 14 and in the groove 14, so that the sizes of the two are close. Although the size of the pyramid structure in the groove 14 is slightly larger, since the groove 14 itself can diffusely reflect light, it has the effect of compensating for the relatively high reflectivity of the larger pyramid structure on light absorption.

[0054] In some embodiments, as Figure 3As shown, the solar cell further includes a functional layer disposed on the first surface 11, with the thickness of the functional layer located within the groove 14 being greater than the thickness of the functional layer located outside the groove 14. Because the groove 14 itself is recessed toward the interior of the silicon substrate 10 relative to the rest of the first surface 11, the overall roughness of the first surface 11 increases. By adjusting the film preparation process in the cell edge region, the thickness of the functional layer within the groove 14 is increased to be greater than that of the functional layer located outside the groove 14, thereby reducing the roughness of the first surface 11. Furthermore, there are more defects within the groove 14 than outside the groove 14. By increasing the thickness within the groove 14, the passivation effect within the groove 14 can be improved, thereby achieving a more balanced passivation effect across the first surface 11.

[0055] In this embodiment, the functional layer includes a first passivation anti-reflection layer. This first passivation anti-reflection layer is provided on first surface 11 to improve the passivation effect of first surface 11, reduce carrier recombination, and reduce sunlight reflection, thereby enhancing the light absorption capacity of first surface 11 and improving the conversion efficiency of the solar cell. Optionally, by adjusting the film preparation process at the cell edge and increasing the thickness of the passivation anti-reflection layer within groove 14, the passivation effect within groove 14 can be improved, thereby achieving a balanced passivation effect across first surface 11.

[0056] For example, in a direction away from the silicon substrate 10, the first passivation anti-reflection layer includes a first aluminum oxide layer 60 and a first silicon nitride layer 70 stacked together. The thickness of the first aluminum oxide layer 60 within the groove 14 is 4.5 nm to 5 nm, specifically 4.5 nm, 4.6 nm, 4.7 nm, 4.8 nm, 4.9 nm, 5 nm, etc., while the thickness of the first aluminum oxide layer 60 outside the groove is 4 nm to 4.5 nm, specifically 4 nm, 4.1 nm, 4.2 nm, 4.3 nm, 4.4 nm, 4.5 nm, etc. The thickness of the first aluminum oxide layer 60 within the groove 14 is greater than the thickness of the first aluminum oxide layer 60 outside the groove. And / or, the thickness of the first silicon nitride layer 70 located within the groove 14 is 68 nm to 73 nm, specifically 68 nm, 69 nm, 70 nm, 71 nm, 72 nm, 73 nm, etc., and the thickness of the first silicon nitride layer 70 located outside the groove is 65 nm to 70 nm, specifically 65 nm, 66 nm, 67 nm, 68 nm, 69 nm, 70 nm, etc. The thickness of the first silicon nitride layer 70 located within the groove 14 is greater than the thickness of the first silicon nitride layer 70 located outside the groove. By setting the thickness of the first aluminum oxide layer 60 and the first silicon nitride layer 70 inside and outside the groove 14, the passivation effects of the first aluminum oxide layer 60 and the first silicon nitride layer 70 are balanced inside and outside the groove, thereby improving the overall passivation effect of the first surface 11.

[0057] Of course, the first passivation anti-reflection layer can also be made of other materials, including silicon oxide, silicon carbide, aluminum oxide, silicon nitride, silicon oxynitride, or titanium oxide. The first passivation anti-reflection layer can be a single layer or a stacked structure composed of one or more of the above materials. As long as passivation can be achieved, the materials are not limited to those listed in this embodiment.

[0058] In some embodiments, as Figure 3 and Figure 4 As shown, the solar cell also includes a doped conductive layer 30 and a second passivation anti-reflection layer disposed on the second surface 15. The second passivation anti-reflection layer is located on the side of the doped conductive layer 30 facing away from the silicon substrate 10. The second passivation anti-reflection layer located on the second surface can passivate the surface of the doped conductive layer 30, reducing carrier recombination at the interface and improving cell efficiency. The second passivation anti-reflection layer also has an anti-reflective effect, improving light utilization. The doped conductive layer 30 is selected and disposed according to the type of solar cell.

[0059] For example, the second passivation anti-reflection layer and the first passivation anti-reflection layer can have the same structure. For example, the second passivation anti-reflection layer includes a second aluminum oxide layer 40 and a second silicon nitride layer 50 stacked in a direction away from the silicon substrate 10. Of course, the second passivation anti-reflection layer can also be made of other materials, including silicon oxide, silicon carbide, aluminum oxide, silicon nitride, silicon oxynitride, or titanium oxide. The second passivation anti-reflection layer can be a single layer or a stacked structure composed of one or more of the above materials. As long as passivation can be achieved, the materials are not limited to those listed in this embodiment.

[0060] The solar cell may be a back-contact cell, a bifacial cell, or the like. The back-contact cell may be an interdigitated back-contact cell, a heterojunction back-contact cell, a tunneling passivation back-contact cell, or a hybrid tunneling passivation and heterojunction back-contact cell. The bifacial cell may be a heterojunction cell, a tunneling passivation cell, or the like. Different cell types employ different materials and structures for the doped conductive layer 30.

[0061] For example, the silicon substrate 10 may be made of N-type or P-type single crystal silicon, polycrystalline silicon, microcrystalline silicon, or the like. The material of the doped conductive layer 30 may include doped single crystal silicon, doped polycrystalline silicon, doped microcrystalline silicon, doped nanocrystalline silicon, doped amorphous silicon, or the like. The materials and doping types of the silicon substrate 10 and the doped conductive layer 30 are appropriately selected according to the cell type. For example, when the doped conductive layer 30 is doped polycrystalline silicon, it may form a tunneling passivation contact structure with the tunneling oxide layer 20. When the doped conductive layer 30 is doped amorphous silicon, it may form a heterojunction contact structure with intrinsic amorphous silicon. The solar cell formed may be a back-contact solar cell or a bifacial solar cell having a tunneling passivation contact structure and / or a heterojunction contact structure, which is not specifically limited here.

[0062] In some embodiments, as Figure 3 As shown, in the case where the doped conductive layer 30 includes one or more of doped polycrystalline silicon, doped microcrystalline silicon, and doped nanocrystalline silicon, the solar cell further includes a tunneling oxide layer 20, which is located between the silicon substrate 10 and the doped conductive layer 30. The tunneling oxide layer 20 and the doped conductive layer 30 constitute a tunneling passivation contact structure, which partially or entirely covers the surface of the silicon substrate 10. The solar cell is a tunneling passivation contact solar cell.

[0063] For a bifacial solar cell, the silicon substrate 10 includes a first surface 11 and a second surface 15. The doped conductive layers on the same surface of the silicon substrate 10 have the same conductivity type, which can be a P-type doped semiconductor layer or an N-type doped semiconductor layer. The doped semiconductor layers with different doping types are located on the first and second surfaces opposite to each other on the silicon substrate, forming a bifacial solar cell with a tunneling passivation contact structure.

[0064] In some embodiments, the tunneling passivation contact structure on the same surface of the silicon substrate 10 can partially cover the surface, forming a certain pattern, such as a stripe pattern arranged at intervals or a cross-shaped pattern. Alternatively, the tunneling passivation contact structure on the same surface of the silicon substrate 10 can cover the entire surface. In a bifacial solar cell, a tunneling oxide layer 20, a doped conductive layer 30, and a second passivation anti-reflection layer are sequentially stacked on the second surface 15 of the silicon substrate 10, and a diffusion layer (not shown) and a first passivation anti-reflection layer are sequentially stacked on the first surface 11 of the silicon substrate 10.

[0065] In a solar cell with a tunneling passivation contact structure, the tunneling oxide layer 20 located between the silicon substrate 10 and the doped conductive layer 30 allows electrons to pass through while blocking hole transmission, thereby achieving efficient charge separation, reducing interfacial recombination losses, and improving interfacial passivation, thereby increasing photoelectric conversion efficiency. Furthermore, the tunneling oxide layer 20 prevents metal crystals from piercing the doped conductive layer 30 and entering the silicon substrate 10, preventing damage to the passivation on the solar cell surface and thus loss of cell efficiency.

[0066] For a back-contact solar cell, the doped conductive layer 30 includes a first doped conductive layer and a second doped conductive layer disposed on the second surface 15 of the silicon substrate 10, wherein the first doped conductive layer and the second doped conductive layer have opposite conductivity types; a second passivation anti-reflection layer covers the first doped conductive layer and the second doped conductive layer, respectively. The first doped conductive layer and the second doped conductive layer can be isolated by a trench or electrically isolated by other means. The tunneling oxide layer 20 located between the silicon substrate 10 and the doped conductive layer 3 can be a whole layer structure, or can correspond to the positions of the first doped conductive layer and the second doped conductive layer, respectively, and be disconnected at the trench position. A first passivation anti-reflection layer is provided on the first surface 11 of the silicon substrate 10.

[0067] When the above technical solution is adopted, a first doped conductive layer and a second doped conductive layer with opposite conductivity types are formed on one surface of the silicon substrate 10, and the first doped conductive layer and the second doped conductive layer both form a tunneling passivation contact structure with the tunneling oxide layer. The solar cell is a back contact cell with a tunneling passivation contact structure, and has the advantages of both a tunneling passivation contact structure and a back contact cell. The positive and negative electrodes of the back contact cell are both located on the back, eliminating the blocking of light by the electrodes, which can increase the short-circuit current and the open-circuit voltage.

[0068] In some embodiments, as Figure 3 and Figure 4 As shown, a doped conductive layer 30 and a second passivation anti-reflection layer are also provided on the first side surface 12. The doped conductive layer 30 partially covers the first side surface 12, and the second passivation anti-reflection layer fully or partially covers the first side surface 12. The doped conductive layer 30 located on the first side surface 12 is in contact with the doped conductive layer 30 located on the second side surface 15. Specifically, the first side surface 12 may be partially covered with the doped conductive layer 30 to form a side Poly region 121, and the first side surface 12 may be entirely or partially covered with the second passivation anti-reflection layer. The second passivation anti-reflection layer is located on a side of the doped conductive layer 30 away from the side surface. After laser heat treatment, the new side surface of the silicon wafer formed by the splitting has a large number of dangling bonds. By covering the first side surface with the second passivation anti-reflection layer, the dangling bonds on the side surface can be saturated, reducing the interface state density, achieving passivation of the side surface, and improving the efficiency of the solar cell.

[0069] In addition, the doped conductive layer 30 located on the first side surface 12 can protect the second side surface 15 from being over-etched. A doped conductive layer 30 connected to the doped conductive layer 30 on the second side surface 15 is provided on the first side surface 12, and passivation protection is performed by a second passivation anti-reflection layer. This can improve the passivation performance of the solar cell while reducing excessive etching of the film layer on the second side by the etching solution. The portion of the second passivation anti-reflection layer on the side surface close to the second side surface 15 can reduce the probability of carrier recombination at the edge of the solar cell, which is beneficial to improving the performance of the solar cell.

[0070] In some embodiments, the area on the first side 12 covered with the doped conductive layer 30 includes at least a plurality of tower base structures, that is, the velvet structure on the area (side Poly region 121) on the first side 12 covered with the doped conductive layer 30 includes at least a plurality of tower base structures. The side Poly region 121 having multiple tower base structures is beneficial for increasing the specific surface area of ​​the first side 12 of the solar cell, thereby increasing the specific surface area of ​​the subsequent coating film layer, and thus improving the passivation effect of the second passivation anti-reflection layer on the first side 12 of the solar cell.

[0071] Optionally, the area on the first side 12 covered with the doped conductive layer 30 includes multiple pyramid structures and multiple tower base structures, specifically a mixed textured structure of pyramid structures and tower base structures, with the tower base structures closer to the second side 15, wherein the tower base structures have a shape that is either square or approximately square, and the top surface of the tower base structures is approximately flat. The area on the first side 12 not covered with the doped conductive layer 30 includes multiple pyramid structures. During the alkaline texturing process on the first side 11, the first side 11 comes into contact with the etching solution, and the majority of the first side 12 near the first side 11 is immersed in the etching solution. The portion of the first side 12 exposed to the surface of the silicon substrate 10 is corroded by the etching solution to form the pyramid structures. The portion of the first side 12 not exposed to the surface of the silicon substrate 10, because the side Poly region and the alkaline etching solution are substantially unreactive under the process conditions, appears as a tower base structure on the side surface of the silicon substrate during texturing. In this manner, by providing the pyramid structures and tower base structures on the side of the solar cell, the light trapping effect of the side is improved, thereby increasing the light absorption of the solar cell. In addition, the passivation performance of the tower base structure in the side Poly area 121 is better after the second passivation anti-reflection layer is plated, and the better passivation performance of the part close to the second surface 15 can reduce the probability of carrier recombination at the edge of the solar cell, which is beneficial to improving the performance of the solar cell.

[0072] The combined process can improve the problem of excessive etching of the second surface 15. In the solar cell of the embodiment of the present application, setting a side Poly area 121 on the first side 12 can improve the passivation performance of the solar cell while reducing excessive etching of the functional layer on the second surface by the etching solution.

[0073] For example, the lateral length of the tower base structure ranges from 10 μm to 30 μm (e.g., 10 μm to 12 μm, 12 μm to 13 μm, 13 μm to 14.5 μm, 14.5 μm to 15 μm, 15 μm to 20 μm, 20 μm to 25 μm, 25 μm to 28 μm, 28 μm to 30 μm, etc.). Specifically, the lateral length of the tower base structure is the maximum distance from the tower base surface of the tower base structure.

[0074] For example, the longitudinal height range of the base of the base structure is 0.01μm to 8μm (such as 0.01μm to 0.05μm, 0.05μm to 0.1μm, 0.1μm to 0.4μm, 0.4μm to 0.5μm, 0.5μm to 0.7μm, 0.7μm to 1μm, 1μm to 1.3μm, 1.3μm to 1.5μm, 1.5μm to 1.8μm, 1.8μm to 2.3μm, 2.3μm to 2.8μm, 2.8μm to 3.3μm, 3.3μm to 4μm, 4μm to 5μm, 5μm to 6μm, 6μm to 7μm, 7μm to 8μm, etc.).

[0075] In some embodiments, the tower base structure is not fully displayed in the side Poly area 121.

[0076] In some embodiments, a boundary line between the side Poly region 121 and the remaining area on the first side surface 12 is a curve, and a pit is provided near the boundary line in the side Poly region 121 .

[0077] In some embodiments, the shape of the pit includes one or more of an inverted pyramid, an inverted hemisphere, and a terrace. The pit can be obtained by a three-dimensional microscope or a scanning electron microscope, and the depth of the pit can be obtained by scanning with a three-dimensional microscope.

[0078] The dimples are located at the junction of the side poly region 121 and the remaining areas of the first side surface 12, creating a transitional topography between the side poly region 121 and the remaining areas. This reduces the apparent unevenness of the first side surface 12 and improves the subsequent coating quality at the junction. Furthermore, the dimples located in the side poly region 121 also partially enhance the light trapping effect of incident light.

[0079] In some embodiments, along the thickness direction of the silicon substrate 10, the width of the doped conductive layer 30 located on the first side surface 12 accounts for 10% to 20% of the thickness of the silicon substrate 10. That is, the distance between the boundary of the side poly region 121 farthest from the second surface 15 and the second surface 15 accounts for 10% to 20% of the thickness of the silicon substrate 10, and can specifically be 10%, 12%, 14%, 16%, 18%, 20%, etc. When the ratio of the width of the side poly region 121 to the thickness of the silicon substrate 10 is less than 10%, the proportion of the side poly region 121 is too small, and the risk of over-etching the functional layer on the second surface 15 increases. When the ratio of the width of the side poly region 121 to the thickness of the silicon substrate 10 is greater than 20%, the proportion of the side poly region 121 is too large, and the side de-plating effect cannot be guaranteed. In this way, the probability of tiny defects between layers caused by the different lateral etching efficiencies between the functional layer and the silicon substrate can be reduced, thereby reducing the problem of compounding in the final battery, improving the passivation effect of the battery, and thus improving the battery efficiency.

[0080] In addition, the solar cell also includes electrodes. The positions of the electrodes are set according to the type of solar cell. For a bifacial cell, electrodes of different polarities are respectively set on the first and second sides of the solar cell. For a back-contact cell, electrodes of different polarities are set on the second side of the solar cell. Based on the solar cell described in any of the above embodiments, an embodiment of the present invention further provides a photovoltaic module, including a cell string, an interconnection member, and an encapsulation layer, wherein the cell string is formed by electrically connecting a number of solar cells as described in any of the above embodiments; the interconnection member is electrically connected to the solar cell; and the encapsulation layer covers the surface of the cell string. The encapsulation layer may include a cover plate and a back plate located on both sides of the cell string, as well as an encapsulation film and other structures for encapsulation. Since the photovoltaic module adopts the solar cell described in any of the above embodiments, the photovoltaic module has the same beneficial effects as any of the above embodiments.

[0081] Example 1

[0082] The following describes how a conventional silicon substrate is laser processed, then split into sliced ​​silicon substrates, and then used to prepare a BC cell. It should be understood that the following description is for comprehension only and is not intended to be limiting.

[0083] Step S1: providing an initial silicon substrate, which may be a large-sized silicon substrate.

[0084] Illustratively, in step S1 above, the initial silicon substrate used may be an intrinsically conductive substrate, an N-type conductive substrate, or a P-type conductive substrate. Preferably, the silicon substrate is an N-type conductive substrate or a P-type conductive substrate. The initial silicon substrate may be a raw silicon substrate obtained by diamond wire sawing of a silicon rod.

[0085] Step S2: using a first laser, such as a nano laser, to open guide grooves from two edges of the original silicon substrate; then using a non-destructive laser to perform heat treatment along the extension direction of the guide grooves, and then splitting to form sliced ​​silicon wafers.

[0086] For example, in the above step S2, the lossless laser adopts nanosecond continuous laser, and the laser moving speed of the lossless thermal cracking laser in the extension direction of the guide groove is 40-60m / s and the laser power is 300-500W.

[0087] Step S3: Use the above-mentioned sliced ​​silicon wafers to prepare BC batteries according to the BC process steps.

[0088] Comparative Example 1

[0089] The difference from Example 1 is that a sliced ​​silicon substrate is used, and the edges of the sliced ​​silicon substrate are not subjected to laser heat treatment.

[0090] In this application, grooves are formed on the edges of the first surface of the heat-treated sliced ​​silicon wafers during the preparation of solar cells. The grooves protect the water film during the wet process of the cell, reducing the need for rework due to excessive surface etching that affects cell performance. Verification data shows that the yield rate of 100,000 cell wafers in the etching process was 95.6% for Example 1 and 95.58% for Comparative Example 1. Compared with Comparative Example 1, Example 1 can achieve a yield improvement of 0.02%, thereby reducing rework by 0.02%.

[0091] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0092] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A solar cell, characterized in that: The silicon substrate includes a first surface and a second surface opposite to each other, and a first side surface connecting the first surface and the second surface; The edge of the first surface connected to the first side surface is a groove area, the groove area has a plurality of grooves, and the plurality of grooves are arranged along the length direction of the edge; The grooves include a plurality of continuous strip-shaped pits or a plurality of discontinuous pits.

2. The solar cell according to claim 1, wherein An included angle is formed between an extending direction of the groove and an edge where the first surface and the first side surface meet, and the included angle ranges from 30° to 70°.

3. The solar cell according to claim 1, wherein In a direction perpendicular to the first side surface, a width of the groove region is less than or equal to 100 μm.

4. The solar cell according to claim 1, wherein In the thickness direction of the silicon substrate, the depth of the groove is less than or equal to 3 μm.

5. The solar cell according to claim 1, wherein The first surface has a plurality of first pyramid structures located in the groove and a plurality of second pyramid structures located outside the groove, and one-dimensional dimensions of the first pyramid structures are greater than one-dimensional dimensions of the second pyramid structures.

6. The solar cell according to claim 1, wherein The solar cell further includes a functional layer disposed on the first surface; the thickness of the functional layer located within the groove is greater than the thickness of the functional layer located outside the groove.

7. The solar cell according to claim 6, characterized in that Along the direction away from the silicon substrate, the functional layer includes a first passivation anti-reflection layer; the first passivation anti-reflection layer includes a first aluminum oxide layer and a first silicon nitride layer stacked; The thickness of the first aluminum oxide layer located in the groove is 4.5 nm to 5 nm, and the thickness of the first aluminum oxide layer located outside the groove is 4 nm to 4.5 nm; And / or, the thickness of the first silicon nitride layer located in the groove is 68 nm to 73 nm, and the thickness of the first silicon nitride layer located outside the groove is 65 nm to 70 nm.

8. The solar cell according to claim 1, wherein The solar cell further includes a doped conductive layer and a second passivation anti-reflection layer disposed on the second surface. The second passivation anti-reflection layer is located on a side of the doped conductive layer facing away from the silicon substrate.

9. The solar cell according to claim 8, characterized in that The solar cell also includes a tunneling oxide layer arranged on the second surface, the tunneling oxide layer is located between the silicon substrate and the doped conductive layer, the tunneling oxide layer and the doped conductive layer constitute a tunneling passivation contact structure, and the tunneling passivation contact structure partially or entirely covers the second surface.

10. The solar cell according to claim 8, wherein The doped conductive layer and the second passivation anti-reflection layer are also provided on the first side surface, the doped conductive layer partially covers the first side surface, the second passivation anti-reflection layer fully or partially covers the first side surface, and the doped conductive layer located on the first side surface is connected to the doped conductive layer located on the second side surface.

11. The solar cell according to claim 10, characterized in that The area on the first side surface covered with the doped conductive layer includes at least a plurality of tower base structures, and the area on the first side surface not covered with the doped conductive layer includes at least a plurality of pyramid structures.

12. The solar cell according to claim 10, characterized in that Along the thickness direction of the silicon substrate, the width of the doped conductive layer located on the first side surface accounts for 10% to 20% of the thickness of the silicon substrate.

13. A photovoltaic module, characterized in that: include: A battery string, wherein the battery string is formed by electrically connecting several solar cells according to any one of claims 1 to 12; an interconnection member, electrically connected to the solar cell; and an encapsulation layer covering the surface of the battery string.

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